Development and characterization of concentric capillary nebulizer used in inductively coupled plasma analysis /
Abstract
A simple, low-cost concentric capillary nebulizer (CCN) was developed and
evaluated for ICP spectrometry. The CCN could be operated at sample uptake rates
of 0.050-1.00 ml min'^ and under oscillating and non-oscillating conditions. Aerosol
characteristics for the CCN were studied using a laser Fraunhofter diffraction
analyzer. Solvent transport efficiencies and transport rates, detection limits, and
short- and long-term stabilities were evaluated for the CCN with a modified cyclonic
spray chamber at different sample uptake rates. The Mg II (280.2nm)/l\/lg 1(285.2nm)
ratio was used for matrix effect studies. Results were compared to those with
conventional nebulizers, a cross-flow nebulizer with a Scott-type spray chamber, a
GemCone nebulizer with a cyclonic spray chamber, and a Meinhard TR-30-K3
concentric nebulizer with a cyclonic spray chamber. Transport efficiencies of up to
57% were obtained for the CCN. For the elements tested, short- and long-term
precisions and detection limits obtained with the CCN at 0.050-0.500 ml min'^ are
similar to, or better than, those obtained on the same instrument using the
conventional nebulizers (at 1.0 ml min'^). The depressive and enhancement effects of
easily ionizable element Na, sulfuric acid, and dodecylamine surfactant on analyte
signals with the CCN are similar to, or better than, those obtained with the
conventional nebulizers. However, capillary clog was observed when the sample
solution with high dissolved solids was nebulized for more than 40 min.
The effects of data acquisition and data processing on detection limits were
studied using inductively coupled plasma-atomic emission spectrometry. The study examined the effects of different detection limit approaches, the effects of data
integration modes, the effects of regression modes, the effects of the standard
concentration range and the number of standards, the effects of sample uptake rate,
and the effect of Integration time. All the experiments followed the same protocols.
Three detection limit approaches were examined, lUPAC method, the residual
standard deviation (RSD), and the signal-to-background ratio and relative standard deviation of the background (SBR-RSDB). The study demonstrated that the different
approaches, the integration modes, the regression methods, and the sample uptake
rates can have an effect on detection limits. The study also showed that the different
approaches give different detection limits and some methods (for example, RSD) are
susceptible to the quality of calibration curves. Multicomponents spectral fitting (MSF)
gave the best results among these three integration modes, peak height, peak area,
and MSF. Weighted least squares method showed the ability to obtain better quality
calibration curves. Although an effect of the number of standards on detection limits
was not observed, multiple standards are recommended because they provide more
reliable calibration curves. An increase of sample uptake rate and integration time
could improve detection limits. However, an improvement with increased integration
time on detection limits was not observed because the auto integration mode was
used.